How to write a formula that uses Numerical constant linked to filter selection (drop down)?

This would be the logic:

e.g.:

Case

when CONTAINS_TEXT(Country drop down,"us") then ((Clicks*0.015*2000)-Cost)

when CONTAINS_TEXT(Country drop down,"uk") then ((Clicks*0.018*1500)-Cost)

ELSE ((Clicks*0.012*1000)-Cost)

END

So far I have been getting an error that dimensions can not be combined with metrics in formulas.

Thanks a million for your help.